Hepatocellular Carcinomas With Mutational Activation of Beta Catenin Require Choline and can be Detected by Positron Emission Tomography

Abstract Background & Aims In one third of hepatocellular carcinomas (HCCs), cancer cells have mutations that activate beta catenin pathway. These cells have alterations in glutamine, bile, and lipid metabolism. We investigated whether positron emission tomography (PET) imaging allows identification of altered metabolic pathways that might be targeted therapeutically. Methods We studied mice with activation of beta catenin in liver ( Apc ko-liv mice) and male C57Bl/6 mice given injections of diethylnitrosamine, which each develop HCCs. Mice were fed a conventional or a methionine- and choline-deficient (MCD) diet or a choline-deficient (CD) diet. Choline uptake and metabolism in HCCs were analyzed by micro-PET imaging of mice; livers were collected and analyzed by histologic, metabolomic, mRNA quantification, and RNA-seq analyses. Fifty-two patients with HCC underwent PET imaging with 18 F-fluorodeoxyglucose (FDG) followed by 18 F-fluorocholine (FHC) tracer metabolites. Human HCC specimens were analyzed by immunohistochemistry, quantitative PCR, and DNA sequencing. We used hepatocytes and mouse tumor explants for studies of incorporation of radiolabeled choline into phospholipids and its contribution to DNA methylation. We analyzed HCC progression in mice fed a CD diet. Results Livers and tumors from Apc ko-liv mice had increased uptake of dietary choline, which contributes to phospholipid formation and DNA methylation in hepatocytes. In patients and in mice, HCCs with activated beta catenin were positive in FCH-PET but not FDG-PET, and they overexpressed the choline transporter organic cation transporter 3. The HCC cells from Apc ko-liv mice incorporated radiolabeled methyl groups of choline into phospholipids and DNA. In Apc ko-liv mice, the MCD diet reduced proliferation and DNA hypermethylation of hepatocytes and HCC cells, and the CD diet reduced long-term progression of tumors. Conclusions In mice and humans, HCCs with mutations that activate beta catenin are characterized by increased uptake of a fluorocholine tracer (FCH), but not FDG, revealed by PET. The increased uptake of choline by HCCs promotes phospholipid formation, DNA hypermethylation, and hepatocyte proliferation. In mice, the CD diet reverses these effects and promotes regression of HCCs that overexpress beta catenin.